CN105813553B

CN105813553B - Devices, systems, and methods for assessing intravascular pressure

Info

Publication number: CN105813553B
Application number: CN201480066580.2A
Authority: CN
Inventors: J·斯蒂加尔
Original assignee: Volcano Corp
Current assignee: Philips Image Guided Therapy Corp
Priority date: 2013-12-06
Filing date: 2014-12-05
Publication date: 2021-03-26
Anticipated expiration: 2034-12-05
Also published as: EP3076864B1; CN105813553A; JP6644687B2; EP3076864A4; JP2017500932A; EP3076864A1; WO2015085220A1

Abstract

Described is an apparatus for intravascular pressure measurement comprising an elongated body, a first pressure sensor, and a centering assembly disposed adjacent the sensor. In one aspect, the elongate body has a uniform diameter from the distal end to the proximal end. In another aspect, the uniform diameter is 0.035 inches or less. In yet another aspect, the elongate body is a catheter having a plurality of reinforcing filaments, and the filaments are utilized to electrically connect the sensor to the proximal end.

Description

Devices, systems, and methods for assessing intravascular pressure

Technical Field

Embodiments of the present disclosure relate generally to the field of medical devices, and more particularly, to a device, system, and method for assessing intravascular pressure. In particular, the present disclosure relates to assessing the severity of a blockage or other restriction in the flow of fluid through a vessel. Aspects of the present disclosure are particularly useful in the assessment of biological vessels in certain circumstances. For example, certain embodiments of the present disclosure are particularly configured for assessing the degree of stenosis of a human blood vessel.

Background

Heart disease is a dangerous health condition affecting millions of people worldwide. One major cause of heart disease is the presence of blockages or lesions within the blood vessels that reduce blood flow through the vessels. Traditionally, surgeons rely on X-ray fluoroscopic (planar) images to show the external shape and contour of blood vessels to guide treatment. Unfortunately, using only X-ray fluorescence images introduces a great deal of uncertainty as to the exact extent and orientation of the lesion causing the occlusion, making it difficult to find the exact location of the stenosis for treatment. Furthermore, fluoroscopy is an inappropriate re-assessment tool for assessing vessels after surgical treatment.

One currently accepted technique for assessing the severity of stenosis in a blood vessel, including lesions resulting from ischemia, is Fractional Flow Reserve (FFR). FFR is defined as the ratio of the maximum blood flow in a stenosed artery taken distal to the lesion to the normal maximum flow. Thus, to calculate FFR for a given stenosis, two blood pressure measurements are taken: a measurement located distal or downstream of the stenosis and a measurement located proximal or upstream of the stenosis. FFR is a calculation of the ratio of the distal pressure measurement relative to the proximal pressure measurement. FFR provides a stenosis severity index that allows a determination of whether the occlusion limits the flow of blood within the vessel to a level that requires treatment. The more restrictive the stenosis, the greater the pressure drop across the stenosis, and the lower the FFR achieved. FFR measurements can be used as a decision point for guiding treatment decisions. The normal value of FFR in healthy vessels is 1.00, while values below about 0.80 are generally considered significant and require treatment. Common treatment options include angioplasty, atherectomy and stenting.

One method of measuring the pressure gradient across the lesion is to use a pressure sensing guidewire with a pressure sensor embedded within the guidewire itself. The user may initially position the pressure sensor of the guidewire distal to the lesion and measure the distal pressure before pulling the guidewire back, thereby repositioning the sensor proximal to the lesion to measure the proximal pressure. This method has the disadvantage of inaccurate pressure readings due to offset and increased sensitivity to temperature variations, difficulty in manipulating the guidewire through occlusions, high manufacturing costs, and time-consuming repositioning steps (particularly where multiple lesions are involved). Furthermore, when compared to large pressure sensing devices such as aortic pressure sensing catheters, pressure sensing guidewires typically suffer from reduced precision and accuracy when making intravascular pressure measurements.

Another method of measuring the pressure gradient across the lesion is to use a small catheter connected to a blood pressure sensor, which is typically contained in a sensor housing associated with the catheter. However, this approach can introduce errors in FFR measurements because as the catheter passes through the lesion, the catheter and the sensor housing itself create additional blockage to blood flow across the lesion and result in a lower distal blood pressure than would be caused by the lesion alone, which can increase the measured pressure gradient across the lesion.

While existing treatments have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects. The apparatus, system, and related methods of the present disclosure overcome one or more of the disadvantages of the prior art.

Disclosure of Invention

In one exemplary embodiment, the present disclosure describes an apparatus for a microcatheter having a pressure sensor and a centering assembly for generally centrally placing the catheter within a vessel of interest. In yet another aspect, a sensing microcatheter has an inner lumen with a diameter large enough to receive a 0.014 inch diameter guidewire and an outer diameter of 0.035 inches or less.

In other embodiments, the present disclosure is generally directed to an apparatus, system, and method for assessing intravascular pressure using a pressure sensing catheter, including, by way of non-limiting example, calculating an FFR value. In certain instances, embodiments of the present disclosure are configured to measure pressure proximal and distal to a stenotic lesion within a vessel. Embodiments of the present disclosure include a pressure sensor embedded in the wall of the conduit or have a movable sleeve that can smooth the outer diameter of the sensing conduit. In certain embodiments, the pressure sensing catheters disclosed herein are configured as a monorail or quick-exchange catheter in which a guidewire exits the catheter body adjacent the distal end. In other embodiments, the pressure sensing catheter disclosed herein is configured as a conventional in-line catheter. The pressure sensing catheters disclosed herein enable a user to obtain pressure measurements using an existing guidewire (e.g., a conventional 0.014 inch guidewire) that can remain properly secured during the pressure measurement procedure. Thus, the pressure sensing catheters disclosed herein enable a user to obtain physiological information about an intravascular lesion upon retraction of the catheter without losing the original position of the guidewire.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory in nature and are intended to provide an understanding of the present disclosure, but are not intended to limit the scope of the disclosure. In this regard, other aspects, features and advantages of the present disclosure will be apparent to those skilled in the art from the following detailed description.

Brief description of the drawings

The drawings illustrate embodiments of the apparatus and methods disclosed herein and, together with the description, serve to explain the principles of the disclosure.

FIG. 1 is a diagrammatic, partial perspective view of a sensing system in accordance with an embodiment of the invention.

FIG. 2 is a diagrammatic, partial side cross-sectional view of a microcatheter sensing system in accordance with an embodiment of the invention.

Fig. 3 shows a cross-section taken along line 3-3 of fig. 2.

Fig. 4 shows a cross-section taken along line 4-4 of fig. 2.

Fig. 5 is a partial side view of a proximal portion of the microcatheter of fig. 2.

Fig. 6 is a partial side view of a proximal portion of the microcatheter of fig. 5.

Fig. 7 is an end view of the microcatheter of fig. 6.

FIG. 8 is a partial cross-sectional view of a sensing microcatheter according to another aspect of the invention.

FIG. 9 is a diagrammatic, partial perspective view of a sensing system in accordance with an embodiment of the invention.

Fig. 10A is a diagrammatic partial perspective view of a sensing system according to a second embodiment of the invention.

FIG. 10B shows a perspective view of an alternative sensing catheter similar to that of FIG. 10A.

FIG. 11 is a partial perspective view of another embodiment of a sensing catheter in accordance with another aspect of the invention.

FIG. 12 is a partial perspective view of another embodiment of a sensing catheter in accordance with another aspect of the invention.

Detailed Description

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described devices, apparatus, and methods, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described in connection with one embodiment may be combined with the features, components, and/or steps described in connection with other embodiments. Further, the dimensions provided herein are for specific examples and it is contemplated that different sizes, dimensions and/or ratios may be used to implement the concepts of the present invention. However, for the sake of brevity, the multiple accumulations of these combinations will not be described separately. For simplicity, in certain instances, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

The present disclosure relates generally to an apparatus, system, and method for using a pressure sensing catheter for evaluating intravascular or intravenous pressure, including, by way of non-limiting example, calculating an FFR value. In certain instances, embodiments of the present disclosure are configured to measure pressure within a vessel proximal and distal to a stenotic lesion. The pressure sensing catheters disclosed herein enable a user to obtain pressure measurements using an existing guidewire (e.g., a conventional 0.014 inch guidewire) that can remain properly secured throughout the pressure measurement process. Thus, the pressure sensing catheters disclosed herein enable a user to obtain physiological information about an intravascular lesion after pulling back the catheter without losing the original position of the guidewire. Further, in one aspect, the sensing microcatheter has an outer diameter of 0.035 inches or less, such that conventional peripheral treatment devices can use the microcatheter as a guide member for positioning the treatment device (e.g., balloon) in place. Still further, the treatment device can be deployed and retracted without moving the microcatheter sensor so that pressure can be sensed after treatment to determine effectiveness.

Fig. 1 illustrates a medical system 100 configured to measure pressure within a tubular structure V (e.g., a blood vessel) according to one embodiment of the present disclosure. In certain embodiments, the medical system 100 is configured to calculate FFR based on the obtained pressure measurements. The system 100 includes a pressure sensing microcatheter 102 having two

sensors

110 and 112 embedded in a distal portion thereof. Fig. 1 shows a pressure sensor 110 embedded in a conduit wall 102. For this and other embodiments disclosed herein, the pressure sensor 110 comprises any type of pressure sensor that is sufficiently pressure resistant to maintain functionality while embedded within the catheter wall. For example, the pressure sensor 110 may include a capacitive sensor, a piezoresistive pressure transducer, a fiber optic pressure sensor such as disclosed in U.S. patent nos. 8298156 and 8485985 and U.S. application nos. 2103/0303914 and 2013/0131523, each of which is hereby incorporated by reference herein in its entirety, a sensor having a silicon backbone, or any other type of pressure sensor having the requisite durability and pressure resistance. In some cases, the sensor 110 includes a sensor element array or a plurality of sensor elements (e.g., a capacitive pressure sensor array). In the illustrated embodiment, the sensor 110 includes a sensor diaphragm assembly. In certain embodiments, the sensor diaphragm assembly includes a body having a groove covered by a flexible diaphragm configured to measure fluid pressure. The diaphragm may flex in response to changes in pressure around the diaphragm, reflecting, for example, changes in blood pressure. The sensor 110 may then measure and transmit the pressure change applied to the diaphragm assembly. Still further, while the illustrated catheter is described in terms of a pressure sensor, it is contemplated that the type of sensing element disposed on the catheter is not a limitation with respect to all teachings of the present invention. More specifically, it is contemplated that while one sensor on the catheter may be a pressure sensor, additional one or more imaging or fluid sensors may be incorporated into the sensors of the present disclosure. For example,

sensors

110 and 112 may be ultrasound transducers capable of imaging the surrounding vessel and/or detecting fluid flow in the vessel, e.g., by intravascular ultrasound (IVUS).

In the illustrated embodiment, the microcatheter is formed with

sensors

110 and 112 utilizing known techniques, such as those found in U.S. Pat. Nos. 6,030,371 and 7,776,380, each of which is hereby incorporated by reference in its entirety. Catheter forming techniques may be used to form the channels, passageways, and electrical conductor members discussed below.

The sensing microcatheter 102 includes a centering assembly 150 configured to extend outwardly from the outer wall of the catheter to engage the surrounding vessel wall and move the sensor away from the vessel wall into the mainstream flow of the vessel for more accurate sensor readings. Referring to fig. 1-4, the centering assembly includes four

positioning wires

152, 154, 156, and 158 positioned evenly around the circumference of the catheter 102. Each of

wires

152, 154, 156, and 158 extends through an

elongate channel

160, 162, 164, and 166 defined in the outer surface of the catheter body. The positioning wire is anchored in the distal end of the channel, such as shown at

locations

153 and 157 in fig. 2. The positioning wire extends through and is slidable within the tubular lumens of the catheter 102 (see fig. 3). The positioning wire is coupled to a circular knob 210 (see fig. 5) that slides linearly along the catheter body 102 within an annular groove 220 to form the steering actuator 200. As the knob 210 is moved in the direction of arrow C, the positioning wires move in the direction of arrow C until they are deformed outwardly adjacent to the channel in the distal end of the catheter body, in a centering configuration a as shown in fig. 1 and 2. When the knob is moved in the opposite direction, the positioning wire is retracted into the channel into the insertion configuration B shown in fig. 2.

In another aspect, the sensing catheter includes a steering mechanism 300 to allow a user to deflect the tip of the catheter, allowing the catheter to be steered into the appropriate vessel or around obstacles. The steering mechanism includes a pull wire 190 (fig. 2) anchored in the distal tip of the catheter body 102 at a location 194. The pull wire 190 slidably extends within the catheter body 102 through a small lumen 192 to the proximal end of the catheter where it is attached to a knob 310. Knob 310 is positioned in an annular groove 320 formed on the outside of the catheter body and is slidable longitudinally along the catheter body. As the knob is moved forward along the catheter body, the pull wire will serve to deflect the distal tip of the catheter.

Sensors

110 and 112 are coupled to proximal treatment section 400 via

electrical conductors

114 and 116. The processing section includes an application specific integrated circuit 410 configured to activate the sensor, receive sensor data, process the sensor data, and provide output to a user through a display 440 or through an LED 430. A battery 420 is also provided within the catheter body 102 to power the ASIC, sensors, display and LEDs. A display or LED may be used to provide battery charging information to the user. A Radio Frequency (RF) coil or antenna 450 may be provided as a means for communicating externally with other devices to provide sensor output or receive control commands, or both. Further, in certain embodiments, the coil may be used for inductive coupling to charge the battery 420 or otherwise power the sensor.

Referring to fig. 5, 6 and 7, the microcatheter 102 has a diameter Dl that is substantially uniform along its entire length. More specifically, the diameter D2 of the centering assembly actuator 210 is the same as Dl. Likewise, the diameter D3 of steering actuator 310 is the same as Dl, and the diameter D4 of the proximal treatment assembly is the same as Dl. Also, in the illustrated embodiment, the guidewire lumen 106 extends from the distal end to the proximal end. In one embodiment, the guidewire lumen 106 is sized to receive a guidewire 105 having an outer diameter of 0.014 inches, and the microcatheter 102 has a maximum outer diameter no greater than 0.035 inches from the distal end to the proximal end.

In use, the guidewire 105 and microcatheter 106 can be used to traverse a variety of obstacles within a patient. In one aspect, the distal end of the microcatheter 106 is significantly more flexible than the guidewire 105. In one use across tortuous vessels or large curves, the guidewire is retracted about 10 centimeters within the microcatheter and the steering assembly is actuated to bend the end of the microcatheter. The catheter is then advanced along the bend into the desired position. Once in the desired location, the guidewire is advanced through the microcatheter to reinforce the assembly. The process may be repeated to advance the assembly in the desired direction. In yet another aspect, the guidewire may have a rigid distal portion capable of facilitating passage of the assembly through an occlusion that would otherwise deflect the tip of the flexible microcatheter. Once in the desired position, the sensor may be used to sense vessel characteristics such as pressure and flow of fluid within the vessel, or to image the interior of the vessel. A treatment device may be advanced over the microcatheter, deployed to treat the vessel and subsequently withdrawn. The sensor within the microcatheter may again be used to sense vessel characteristics to determine whether the treatment was successful.

Referring now to fig. 8, an alternative form of sensing microcatheter is shown. Microcatheter 800 includes a sensor 810 and a series of layers of reinforcing fibers surrounding an inner guidewire lumen 804. The sensor is electrically connected to a conductive reinforcing filament 814 via a conductor 812 and the filament 814 is encapsulated by an insulating polymer. Likewise, a conductor 820 connects the sensor to a conductive filament 822 encapsulated by an insulating polymer 824. Finally, a conductor 830 connects the sensor 810 to a conductive filament 832. The exterior of the catheter body is completed by being coated with an insulating polymer layer 834. The resulting structure provides a fiber reinforced microcatheter having three conductive strips extending the length of the catheter.

Referring now to fig. 9-12, the disclosed embodiments relate generally to an apparatus, system, and method for using a pressure sensing catheter for evaluating intravascular pressure, including, by way of non-limiting example, calculating an FFR value. In certain instances, embodiments of the present disclosure are configured to measure pressure proximal and distal to a stenotic lesion located within a vessel. Embodiments of the present disclosure include a pressure sensor embedded in the wall of the conduit or have a movable sleeve that can smooth the outer diameter of the sensing conduit. In certain embodiments, the pressure sensing catheter disclosed herein is configured as a monorail or quick-exchange catheter in which the guidewire exits the catheter body adjacent the distal end. In other embodiments, the pressure sensing catheters disclosed herein are configured as a conventional over-the-wire catheter. The pressure sensing catheters disclosed herein enable a user to obtain pressure measurements using an existing guidewire (e.g., a conventional 0.014 inch guidewire) that can remain properly secured during the pressure measurement procedure. Thus, the pressure sensing catheters disclosed herein enable a user to obtain physiological information about an intravascular lesion upon retraction of the catheter without losing the original position of the guidewire.

Fig. 9 illustrates a medical system 900 configured to measure pressure within a tubular structure V (e.g., a blood vessel) according to one embodiment of the invention. In certain embodiments, medical system 900 is configured to calculate FFR based on the obtained pressure measurements. The system 900 includes a pressure sensing catheter 960 interconnected with a processing and communication system 930 communicatively coupled to the user interface 910.

Fig. 9 shows pressure sensor 970 embedded in catheter wall 984. For this and other embodiments disclosed herein, pressure sensor 970 comprises any type of pressure sensor that is sufficiently pressure resistant to maintain functionality while embedded within catheter wall 984. For example, the pressure sensor 970 may comprise a capacitive sensor, a piezoresistive pressure transducer, a fiber optic pressure sensor such as disclosed in U.S. patent nos. 8298156 and 8485985 and U.S. application nos. 2103/0303914 and 2013/0131523, each of which is hereby incorporated by reference herein in its entirety, a sensor having a silicon backbone, or any other type of pressure sensor having the requisite durability and pressure resistance. In some cases, sensor 970 includes an array of sensor elements or a plurality of sensor elements (e.g., an array of capacitive pressure sensors). In the illustrated embodiment, the sensor 970 includes a sensor diaphragm assembly. In certain embodiments, a sensor diaphragm assembly includes a body having a groove covered by a flexible diaphragm configured to measure fluid pressure. The diaphragm may flex in response to changes in pressure around the diaphragm, reflecting, for example, changes in blood pressure. The sensor 970 may then measure and transmit the pressure change exerted on the diaphragm assembly. Still further, while the illustrated catheter is described in terms of a pressure sensor, it is contemplated that the type of sensing element disposed on the catheter is not a limitation with respect to all teachings of the present invention. More specifically, it is contemplated that while one sensor on the catheter may be a pressure sensor, additional one or more imaging or fluid sensors may be incorporated into the sensors of the present disclosure. For example,

sensors

970 and 972 may be ultrasonic transducers capable of imaging the surrounding vessel, e.g., by intravascular ultrasound (IVUS), and/or detecting fluid flow in the vessel.

In the illustrated embodiment, the sensor 970 is positioned within a sensor recess defined within the wall of the catheter. In certain embodiments, the sensor 970 is in intimate contact with the wall. The sensor may be coupled to the catheter wall using any of a variety of known attachment methods, including, by way of non-limiting example, welding, biocompatible adhesives, and/or mechanical fasteners. For example, in one embodiment, the sensor is adhesively bonded to the sensor recess using Loctite glue (Loctite)3311 or any other biocompatible adhesive. In certain embodiments, the sensor may be integrally formed with the conduit wall. In certain embodiments, the sensor recess may be radiopaque.

In one aspect, the sensing catheter 960 is coupled to the processing and communication system 930 such that the elongate catheter extension body 966 engages the housing 934, while the conductors 968 are electrically coupled to an Application Specific Integrated Circuit (ASIC) 936. A battery 938 powers the ASIC 936 and a transmitter 940 that communicates wirelessly with the user interface 910 in standard formats such as WiFi and bluetooth. The ASIC 936 can provide an excitation signal along conductors 968 to

sensors

970 and 972. In one aspect, the

sensors

970 and 972 are resistive pressure sensors and the ASIC 936 receives analog signals from the sensors, processes the signals, and provides digital signals to the transmitter 940. In one aspect, the proximal end 962 of the catheter 962 is integrally formed with the processing and communication system 930 such that the end wall 932 extends directly from the catheter body 966 into an enlarged housing region 934 that houses the power, processing and communication components of the system. It will be appreciated that the catheter including the communication and processing system 930 may have an integral waterproof outer surface surrounding these components, and the entire system may be made as a single use disposable.

The user interface 910 includes a wireless communication receiver 918 configured to receive signals from a transmitter 940. The user interface includes a processing component (not shown) that can control the display 916 and receive user inputs from the buttons 912 and 914. In one form, the raw data provided by the catheter system is displayed directly on the display 916. In another form, the user interface 910 is controlled by the user through inputs 912 and 914 to collect sufficient data to calculate Fractional Flow Reserve (FFR) of the vessel and display this information to the user.

The catheter 960 includes an intermediate portion 966 that includes an elongated flexible tubular body extending from the proximal portion 962 to the distal sensing portion 964. The body 966 includes a catheter wall defining an interior lumen configured to receive the conductor 968. In the illustrated embodiment, the intermediate portion 966 has a diameter 967 that is smaller than a diameter 965 of the distal portion 964. The distal portion 964 includes two embedded

sensors

970 and 972. Although two sensors are shown for illustrative purposes, in some applications only a single sensor is required, while in other applications multiple sensors may be required. The exterior of

sensors

970 and 972 is not larger than diameter 965 of distal portion 964 and is substantially flush with the exterior surface.

The distal portion 964 is constructed by first providing an inner catheter portion 982 that defines a guidewire lumen 980 configured to receive the guidewire 150.

Sensors

970 and 972 are mounted on the exterior of the inner catheter 982 and electrically connected to the conductor 968. The outer conduit portion 984 is then positioned to surround the inner conduit 982. The outer catheter includes a pair of openings sized to receive

sensors

970 and 972. In one form, the outer catheter 984 is positioned with an opening adjacent the sensor and then heat shrunk to match the outer diameter of the inner catheter 982. In a preferred form, the outer catheter 984 has a material thickness after heat shrinking that is at least as thick as the

sensors

970 and 972, the

sensors

970 and 972 extending outwardly from the surface of the inner catheter 982. Thus, as the sensing catheter is advanced within the patient along the guidewire, the sensor will be protected and will not form a ledge that may catch on the patient's anatomy.

In general, the catheter 960 is sized and shaped for use within an internal structure of a patient, including, but not limited to, arteries, veins, ventricles, nerve and vessel structures, the gastrointestinal system, the pulmonary system, and/or other areas requiring internal access to anatomical structures within the patient. In the illustrated embodiment, the catheter 960 is shaped and sized for intravascular placement.

In particular, the catheter 960 is shaped and configured for insertion into the lumen of a blood vessel V such that the longitudinal axis of the catheter is aligned with the longitudinal axis of the vessel at any given location within the vessel lumen. In this regard, the straight configuration shown in fig. 9 is for exemplary purposes only, and is in no way limiting of the manner in which the conduit may otherwise be bent. In general, the elongated body can be configured to exhibit any desired arcuate profile when in the bent configuration. The catheter is formed of a flexible material such as, by way of non-limiting example, a plastic, high density polyethylene, Polytetrafluoroethylene (PTFE), nylon, a block copolymer of polyamide and polyether (e.g., PEBAX), a thermoplastic, polyimide, silicone, an elastomer, a metal, a shape memory alloy, a polyolefin, a polyetherester copolymer, polyurethane, polyvinyl chloride, combinations thereof, or any other suitable material for making a flexible elongate catheter.

Referring now to FIG. 10A, another embodiment of a sensing catheter in accordance with the present invention is shown. Fig. 10A illustrates a medical system 1200 configured to measure pressure within a tubular structure V (e.g., a blood vessel) according to one embodiment of the present disclosure. In certain embodiments, the medical system 1200 is configured to calculate FFR based on the obtained pressure measurements. The system 1200 includes a pressure sensing conduit 1260 interconnected with a processing and communication system 1230. In one aspect, the sensing catheter 1260 is coupled to the processing and communication user interface 1230 such that the elongate catheter extension body 1266 engages the housing 1234, and the conductors 1268 are electrically coupled to an application specific integrated circuit (AS IC)1236 disposed within the housing 1234. A battery 1238 powers the ASIC 936 and the display 1216. In one form, the housing 1234 may also contain a transmitter that wirelessly communicates with another user interface or other system components in a standard format such as WiFi or bluetooth. ASIC 1236 is capable of providing excitation signals to

sensors

1270 and 1272 along conductor 1268. In one aspect, the

sensors

1270 and 1272 are resistive pressure sensors and the ASIC 1236 receives analog signals from the sensors, processes the signals, and provides digital signals to the display 1216. In one aspect, the proximal portion 1262 of the catheter 1260 is integrally formed with the processing and communication system user interface 1230 such that the housing 1234 extends directly from the catheter body 1266 as an enlarged housing region that houses the power, processing and communication components of the system. It will be appreciated that the catheter including the communication and processing system user interface 1230 may have an integral waterproof outer surface surrounding these components, and the entire system may be made as a single use disposable item.

The user interface 1230 includes an ASIC component 1236 that activates one or

more sensors

1270 and 1272, receives signals from the sensors, processes the sensor data, and outputs the results to the display 1216 (and wirelessly transmits if needed). In one form, the raw data provided by the catheter system is displayed directly on the display 1216. In another form, the user interface 1230 is controlled by the user through the input 912 to collect sufficient data to calculate Fractional Flow Reserve (FFR) of the vessel and display this information to the user. In one example, when the catheter is positioned at a first vascular location, the user input 1212 is pressed to obtain sensor data for a reference pressure. Then at a more distal vessel location, another button 1212 is pressed to obtain distal pressure. Using the user interface, the processor 1236 is then utilized to determine FFR for the distal vessel location. The results of the FFR are then displayed to the user on display 1216. In the illustrated embodiment, the entire system is powered by a battery 1238. In one aspect, the user interface 1230 may include an induction coil to allow charging of the battery.

The catheter 1260 includes an intermediate portion 1266 that includes an elongated flexible tubular body extending from a proximal portion 1262 to a distal sensing portion 1264. The body 1266 includes a catheter wall that defines an internal cavity configured to receive a conductor 1268. The distal portion 1264 includes two embedded

sensors

1270 and 1272. Although two sensors are shown for illustrative purposes, in some applications only a single sensor is required, while in other applications multiple sensors may be required. The exterior of the

sensors

1270 and 1272 is no larger than the diameter 1265 of the distal portion 1264 and is substantially flush with the outer surface. The distal section of the distal portion 1264 defines a tapered outer surface 1282 that transitions from the cylindrical section 1284 containing the sensor to a distal tip having a guidewire lumen 1280 configured to receive a guidewire 1250. The tapered outer surface has an outer diameter 1267 that is smaller than diameter 1265.

Referring now to FIG. 10B, the sensing catheter is shown having the same features as shown in FIG. 10A, except that sensors 1270 'and 1272' are positioned along a tapered surface 1282. As shown, the sensor is embedded into the catheter such that the sensor does not protrude outward from the tapered surface.

Referring now to FIG. 11, yet another embodiment of a sensing catheter in accordance with another aspect of the present invention is shown. The sensing catheter 1300 includes an inner catheter 1310 that defines a lumen 1312 configured to receive a guidewire 1350. A pair of

sensors

1314 and 1316 are mounted on the outside of catheter 1310 and extend outwardly therefrom. The sensor is electrically connected to an ASIC 1390, which ASIC 1390 is capable of processing analog signals from the sensor and transmitting corresponding data signals to the proximal end of the catheter. Outer catheter 1330 fits around inner catheter 1310. The proximal portion 1370 is fixed relative to the inner catheter 1310, while the distal portion 1332 is movably mounted on the inner catheter. A centering assembly 1360 is defined by the outer catheter between the proximal portion 1370 and the distal portion 1332. In the illustrated embodiment, the centering assembly 1360 includes a plurality of elongated

deformable legs

1362, 1364, and 1366 defined by cutting elongated apertures into the outer conduit 1330. A pair of

pull wires

1340 and 1342 extend through lumens within outer catheter 1330, span the centering assembly and are anchored in distal portion 1332 at

anchor points

1344 and 1346, respectively. The distal portion 1332 includes a pair of

channels

1334 and 1336 sized to slidably receive the

sensors

1314 and 1316, respectively, protruding from the inner catheter 1310. The entrance of each

groove

1334 and 1336 begins in a tapered end 1338.

In operation, the catheter assembly is initially in an insertion configuration with the distal portion 1332 extended to position a, in which the centering assembly is in a collapsed configuration with an outer diameter substantially matching the diameter Dl. In one aspect, the material of outer catheter 1330 is sufficiently resilient such that the centering assembly is biased to return to the collapsed configuration when no force is applied to pull

wires

1340 and 1342. The hub is advanced over the guide wire 1350 to position the sensor in the desired location. When a force is applied to the

pull wires

1340 and 1342 in the direction of arrow C, the distal portion 1332 slides longitudinally along the inner catheter 1310 to position B to expose the

sensors

1314 and 1316. Since the distal portion 1370 of the outer catheter is fixed relative to the inner catheter, the

elongate legs

1362, 1364, and 1366 (along with the fourth leg, not shown) are deformed outward to the centered configuration shown in fig. 11. In this centering configuration, the leg has an outer diameter D2 that is substantially greater than the diameter Dl. Thus, as shown, the centering assembly centers the sensor in the middle of the vessel V. The deformable legs are sized to limit their effect on blood flow in the vessel. In this way, the sensor is positioned in a desired location within the vessel to obtain an optimal reading of the fluid, the reading including characteristics such as pressure and flow rate.

Referring now to fig. 12, yet another embodiment of a sensing catheter 1400 is shown having a sensor 1414 disposed on a distal catheter body 1410 that defines a guidewire lumen 1412 that receives a guidewire 1450. The catheter 1400 includes a centering assembly 1460 that includes a distal ring 1464 slidably mounted on a distal catheter body 1410 and a proximal ring 1462 secured to the catheter body 1410. A plurality of

guidewires

1466, 1468, and 1470 (others on the dorsal side not shown) interconnect the distal and proximal rings. A puller wire 1474 extends through the proximal catheter body 1472 into the distal catheter body 1410 and is connected to the distal loop 1464 at anchor points 1476. Tension applied to pull wire 1474 in the direction of arrow C moves distal ring 1464 toward proximal ring 1462, thereby deforming

wires

1466, 1468, and 1470 outward to the centered configuration shown in fig. 12. In the centering configuration, in which the distal ring 1464 is positioned in position B, the assembly has an outer diameter D2 'that is much greater than the diameter Dl' of the assembly in the insertion configuration.

Wires

1466, 1468, and 1470 are resilient and bias the assembly into a retracted insertion configuration in which the distal ring is positioned in position a. In the illustrated embodiment, the centering assembly is mounted on the exterior of the tube 1410, however, it is contemplated that in alternative embodiments, an annular groove may extend around the tube 1410 such that in the collapsed position, the centering assembly has a maximum outer diameter that is less than or equal to the diameter of the tube 1410.

With reference to the above embodiments, the guidewire lumen includes an inner diameter sized and shaped to receive a passageway of a standard guidewire. The inner diameter may vary from 0.014 inches to 0.40 inches. In one embodiment, the inner diameter is 0.016 inches to slidingly receive a guidewire of 0.014 inches in diameter. In one embodiment, the inner diameter is 0.024 inches. In one embodiment, the inner diameter is 0.018 inches. In another embodiment, the inner diameter is 0.038 inches to accommodate a guidewire having a diameter of 0.035 inches. The catheter includes an outer diameter sized and shaped to traverse a body passageway. In the illustrated embodiment, the outer diameter is sized to allow passage of the catheter through a vascular pathway. In some cases, the body has an outer diameter ranging from 0.014 inches to 0.050 inches, as described above. In one embodiment, the outer diameter is 0.024 inches and the inner diameter is about 0.016 inches. In one embodiment, the outer diameter is 0.018 inches. In another embodiment, the outer diameter is 0.035 inches.

Those skilled in the art will appreciate that the embodiments covered by the present disclosure are not limited to the specific exemplary embodiments described above. In this regard, while the illustrated embodiments have been shown and described, a number of modifications, changes, and substitutions are contemplated in the foregoing disclosure. For example, the pressure sensing catheters disclosed herein may be utilized anywhere where a patient's body, including arterial and venous blood vessels, has a representation for pressure measurement. It is understood that such changes may be made to the above without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the disclosure.

Claims

1. An apparatus for intravascular pressure measurement, comprising:

an elongate body comprising a proximal portion and a distal portion, the body defining a lumen extending from a proximal end to a distal end of the body, the lumen being sized and shaped to allow a guidewire to pass therethrough, the body comprising an annular wall extending from the lumen to an outer surface of the body;

a pressure sensor disposed within a wall of the distal portion of the body; and

a centering assembly disposed adjacent the pressure sensor, the centering assembly having a retracted position and an extended position, the centering assembly adapted to engage a vessel wall to center the pressure sensor within the vessel in the extended position, wherein the centering assembly comprises a plurality of positioning wires positioned evenly about a circumference of the body, each of the positioning wires extending through an elongate channel defined in an outer surface of the body to engage the vessel wall, anchored in a distal end of the channel, the positioning wires extending through and slidable within a lumen of the body proximal of the respective elongate channel.

2. The apparatus of claim 1, wherein an outer surface of the sensor and an outer surface of the body are substantially aligned to form a smooth outer surface.

3. The apparatus of claim 1, wherein the outer surface of the body has a proximal diameter and the body has at least one distal taper having a reduced diameter adjacent the respective distal portion.

4. The apparatus of claim 1, wherein the centering assembly comprises at least three outwardly extending legs.

5. The apparatus of claim 1, wherein the positioning wire is coupled to a knob configured to slide linearly along the body within an annular groove defined within the body.

6. The apparatus of claim 1, wherein the centering assembly is recessed within the outer surface of the body when in the retracted position.

7. The apparatus of claim 2, wherein the pressure sensor is embedded on an annular wall of the body.

8. The apparatus of claim 1, wherein the outer surface of the body has a diameter of 0.035 inches or less.

9. The apparatus of claim 8, wherein the lumen has an inner diameter of at least 0.014 inches, and the pressure sensor is disposed between the lumen and the outer surface.

10. The apparatus of claim 1, wherein the elongated body has a length of at least 50 centimeters.

11. The apparatus of claim 1, further comprising a plurality of stiffening wires extending along a length of the elongate body, at least one wire electrically connected to the pressure sensor.

12. The apparatus of claim 1, further comprising a plurality of pressure sensors disposed within the wall of the distal portion of the body.

13. The apparatus of claim 1, wherein the apparatus is configured such that movement of the positioning wire in a distal direction relative to the elongate body causes the positioning wire to deform outwardly adjacent the channel to assume the extended position of the centering assembly.